Evaluation and interpretation of data obtained with immunoassays and DNA-DNA hybridization techniques

During the last decade several new analytical techniques have been developed for testing food products and clinical samples. One technique uses sensitive immunoassays such as enzyme-linked immunosorbent assay (ELISA) and latex agglutination. The most important step in developing sensitive immunoassays is the evaluation of the assay for specificity, cross-reactivity and sensitivity. False-negative results can easily be detected by adding known quantities of antigen to the sample. The most appropriate way to detect false-positive results is the specific inhibition of the immunological reaction by addition to the test-sample of either synthetic epitopes or anti-idiotype antibodies. The progress in recombinant DNA techniques now offers opportunities for application as analytical tools in food and clinical microbiology. Methods are being developed to detect microorganisms by their nucleic acid sequence using the so-called hybridization procedure. With this technique, labelled DNA fragments (probes) are hybridized with a complementary base sequence present in the microorganism. Foodborne pathogens can be detected by using a probe with a complementary base sequence which codes for toxin production. DNA-DNA hybridization techniques may replace the traditional cultural techniques for assaying pathogenic micro-organisms. However, more experience with these techniques is needed before further evaluation can be given.